1. Field of the Invention
The present invention relates to a high-voltage variable resistor for use, for example, in adjusting the focus voltage and the screen voltage of a television receiver or other such apparatus.
2. Description of the Related Art
Conventionally, high-voltage variable resistors called xe2x80x9cfocuspacksxe2x80x9d are used to adjust the focus and brightness of color televisions, display monitors, and other such apparatuses. Japanese Unexamined Patent Application Publication No. 7-235402 discloses this type of high-voltage variable resistor in which a snap-in terminal having a spring portion to be contacted with a connecting electrode of a circuit board is placed in a terminal base portion of an insulating casing, and an output lead wire is press-fitted in the snap-in terminal in a perpendicular arrangement, thereby establishing a connection to the outside. This high-voltage variable resistor can be produced for low cost because the inner circuit board and the output lead wire can be electrically connected without using a conductive rubber or solder.
In the above-described high-voltage variable resistor, since the snap-in terminal is held in the terminal base portion of the casing, the terminal base portion has an insertion groove for holding both sides of the snap-in terminal, and also has an insertion hole extending perpendicular to the insertion groove so as to insert the output lead wire therein.
In order to precisely press-fit the output lead wire into a hole of the snap-in terminal, the insertion hole must be formed in precise alignment with the insertion groove.
Referring to FIG. 1, an insertion groove 2 and an insertion hole 3 that is perpendicular thereto can be simultaneously formed in a terminal base portion 1 by a metal mold 4 of the structure to be pressed shown in FIGS. 2A and 2B or by a metal mold 5 of the structure to be pierced shown in FIG. 3.
In the metal mold 4 of the structure to be pierced, a first mold 4a for forming the insertion groove 2 and a second mold 4b for forming the insertion hole 3 are simply contacted with each other. Therefore, the center axis of the second mold 4b does not always coincide with a required center line X, as shown in FIG. 2A, and the second mold 4b becomes displaced from the center line X by an amount xcex4 due to pressure of resin, as shown in FIG. 2B. As a result, the insertion hole 3 cannot be formed at a precise position corresponding to the required center line X.
In contrast, in the metal mold 5 of the structure to be pierced, the leading end of a second mold 5b for forming the insertion hole 3 is pierced in a hole 5a1 of a first mold 5a for forming the insertion groove 2. Therefore, the second mold 5b is held at a fixed position by the first mold 5a even when pressure of resin or other source acts thereon, and as a result, the insertion hole 3 can be precisely formed along the required center line X.
Such use of the metal mold of the structure to be pierced provides the advantage of precisely forming the insertion hole 3, but causes a problem. That is, since a clearance lies between the hole 5a1 of the first mold 5a and the second mold 5b, a burr is formed at the rim of the insertion hole 3 opening toward the insertion groove 2 due to the clearance. The burr protrudes toward the inner surface of the insertion groove 2 and interferes with the insertion of the snap-in terminal into the insertion groove 2. This makes it impossible to insert the snap-in terminal to a predetermined position, and to establish a reliable connection between the snap-in terminal and the output lead wire.
In order to overcome the problems described above, preferred embodiments of the present invention provide a high-voltage variable resistor in which an insertion hole can be formed at a precise position so as to be substantially perpendicular to an insertion groove and in which a snap-in terminal can be constantly inserted to a fixed position in the insertion groove without any burrs being formed.
According to a preferred embodiment of the present invention, a high-voltage variable resistor includes an insulating casing with a terminal base portion, a circuit section contained in the casing, a snap-in terminal inserted in the terminal base portion of the casing and connected to an output portion of the circuit section, and an output connecting electrode inserted in the terminal base portion from a direction that is substantially perpendicular to the snap-in terminal and press-fitted in and connected to the snap-in terminal, wherein the terminal base portion of the casing has an insertion groove for guiding and inserting the snap-in terminal, an insertion hole for guiding and inserting the output connecting electrode, and a relief groove provided on a side surface of the insertion groove intersecting the insertion hole, and the insertion groove, the insertion hole, and the relief groove are simultaneously formed by a metal mold of the structure to be pierced.
A mold for forming the insertion groove and the relief groove and a mold for forming the insertion hole are fitted in a pierced manner, and the terminal base portion is integrally molded in this state. When the molds are separated after molding, a molding burr is formed at the intersection of the insertion groove and the insertion hole. Since the burr is formed at the relief groove, it does not interfere with the insertion of the snap-in terminal into the insertion groove. For this reason, the snap-in terminal can be easily inserted into the fixed position, and an unreliable connection between the snap-in terminal and the output connecting electrode is reliably prevented.
Preferably, the output connecting electrode is a snap-in lead wire. That is, by using a snap-in lead wire as an output terminal of the high-voltage variable resistor and press-fitting a core wire of the lead wire into the snap-in terminal via the insertion hole, connection to an external device is reliably and easily established.
Preferably, the metal mold of the structure to be pierced includes a first mold for defining the insertion groove and a second mold pierced in a hole formed in the first mold so as to define the insertion hole, and the depth of the relief groove is preferably substantially equal to or larger than that of the hole formed in the first mold. That is, the thickness of a burr formed by metal mold of the structure to be pierced will not be larger than that of the hole to be pierced. Therefore, the burr and the snap-in terminal are reliably prevented from interfering with each other by setting the depth of the relief groove to be larger than the depth of the hole to be pierced.
Further elements, characteristics, features, and advantages of the present invention will become apparent from the following description of preferred embodiments with reference to the attached drawings.